linux-kernel - Re: [PATCH 12/13] iommu/vt-d: No need to migrating irq for VT-d Posted-Interrtups

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Date:	Tue, 11 Nov 2014 21:48:44 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Feng Wu <feng.wu@...el.com>, gleb@...nel.org, pbonzini@...hat.com,
	dwmw2@...radead.org, joro@...tes.org, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org
CC:	kvm@...r.kernel.org, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/13] iommu/vt-d: No need to migrating irq for VT-d Posted-Interrtups



On 2014/11/10 14:26, Feng Wu wrote:
> We don't need to migrate the irqs for VT-d Posted-Interrtups here.
> When 'pst' is set in IRTE, the associated irq will be posted to
> guests instead of interrupt remapping. The destination of the
> interrupt is set in Posted-Interrupts Descriptor, and the migration
> happens during VCPU scheduling.
> 
> Signed-off-by: Feng Wu <feng.wu@...el.com>
> ---
>  drivers/iommu/intel_irq_remapping.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
> index 87c02fe..249e2b1 100644
> --- a/drivers/iommu/intel_irq_remapping.c
> +++ b/drivers/iommu/intel_irq_remapping.c
> @@ -1038,6 +1038,13 @@ intel_ioapic_set_affinity(struct irq_data *data, const struct cpumask *mask,
>  	if (get_irte(irq, &irte))
>  		return -EBUSY;
>  
> +	/*
> +	 * If the interrupt is for posting, it is used by guests,
> +	 * we cannot change IRTE here.
> +	 */
> +	if (irte.irq_post_low.pst == 1)
> +		return 0;
Hi Feng,
	You should return some error code instead of 0, otherwise the
irq core will get confused.

> +
>  	err = assign_irq_vector(irq, cfg, mask);
>  	if (err)
>  		return err;
> 
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